1. Field of the Invention
The present invention relates to an image forming apparatus. More specifically, the present invention relates to an image forming apparatus in which one of a non-inverted image and an inverted image is formed by developing an electrostatic latent image formed on a surface of a photosensitive member being charged in one of a positive polarity and a negative polarity.
2. Description of the Prior Art
In such a kind of image forming apparatus, at a time just after an image forming mode is changed between a non-inverted image forming mode and an inverted image forming mode by changing a charging polarity of the photosensitive member, a charged voltage of the photosensitive member at the start of a succeeding image forming mode is small due to an influence of a preceding image forming mode.
Therefore, in Japanese Patent Application Laying-open No. 1-294057 laid open on Nov. 28, 1989, it is proposed that an image forming process is started after the photosensitive member is charged in advance (pre-charged) for a predetermined time with a charging polarity adapted to the succeeding image forming mode. However, an image forming apparatus disclosed in the above described prior art, a pre-charge time is required, and therefore, there was a problem that it takes a long time until the image forming process is started.